1. Field of the Invention
The present invention relates to a fluid filled vibration damping device affording vibration damping action on the basis of flow and pressure action of a non-compressible fluid sealed therein, and more particularly to a fluid filled vibration damping device of novel construction, suitable for use in an automotive engine mount, body mount or the like, for example.
2. Description of the Related Art
Among vibration damping couplings or mounts for installation between members that make up a vibration transmission system, one type known in the art is a fluid filled vibration damping device having a first mounting member and a second mounting member connected by a rubber elastic body, as well as having a fluid chamber in which is sealed a non-compressible fluid. The device can exhibit damping effect with respect vibration input across the first and second mounting members, by utilizing flow and pressure action of the non-compressible fluid. In such fluid filled vibration damping devices, the fluid chamber is typically partitioned into a number of zones by partition members, to give a design whereby fluid flow action and pressure transmission action among the several zones are utilized to exhibit more enhanced damping effect.
When installing a partition member in order to partition the fluid chamber, it is advantageous to employ a structure that uses the second mounting member of generally cylindrical shape, whose one of axially opposite openings is provided with a fluid-tight closure by the first mounting member elastically connected thereto by means of the rubber elastic body, and whose the other one of axially opposite openings is integrally formed with a shoulder portion and a large-diameter cylindrical caulking portion, and is provided with a fluid-tight closure by the partition member and a lid member whose outside peripheral portions are superimposed on and fixed caulkwise onto the shoulder portion by pressingly bending the cylindrical caulking portion against the shoulder portion in the process of caulking fixation.
In order to rapidly fill the fluid chamber with non-compressible fluid, it is advantageous to employ an arrangement wherein an annular fixing member disposed on the outside peripheral portion of the lid member is secured by press fitting into the cylindrical caulking portion of the second mounting member, while immersed in a mass of a non-compressible fluid so as to provide a fluid-tight closure to the fluid chamber, and then the second mounting member is removed from the non-compressible fluid in order to perform the aforesaid caulking fixation process on the cylindrical caulking portion in the air.
In the conventional fluid filled vibration damping device of this construction, however, the partition member needs to be press fitted into the cylindrical caulking portion and positioned in an axis-perpendicular direction of the second mounting member, as needed in the fixation member, in the process of caulking fixation of the outside peripheral portion of the partition member together with the fixing member to the cylindrical caulking portion of the second mounting member. That is, during assembly, the two members, i.e., the partition member and the fixing member, must be fitted successively into the cylindrical caulking portion while immersed in the mass of the non-compressible fluid, resulting in a laborious operation.
Additionally, where the number of components fixed caulkwise to the second mounting member at the cylindrical caulking portion is increased to two, or three or more, direct superimposition and caulkwise fixing of these components at the cylindrical caulking portion may be undesirable in some instances, due to problems in the caulking operation, such as problems with dimensional accuracy, assuring adequate caulking force, or the like.
In order to position the partition member in the axis-perpendicular direction with respect to the second mounting member, it would be conceivable, for example, to insert the partition member into the interior of the second mounting member so as to fit against an inner circumferential surface of the second mounting member as disclosed in Citation 1. However, the disclosed structure have the substantially entire partition member inserted into the second mounting member inwardly in the axial direction, inevitably decreasing the axial spacing between the partition member and the rubber elastic body, making it difficult to assure adequate capacity of the fluid chamber.
[Citation 1]
JP-U-2-119540
It would also be conceivable to form an annular stepped recess extending in the circumferential direction on the plane of the shoulder portion of the second mounting member, and to position the outside peripheral portion of the partition member (having smaller diameter than the cylindrical caulking portion) fitting against this stepped recess. However, since it is difficult to make the stepped recess very large, this arrangement makes it difficult to determine whether the partition member is positioned within the stepped recess, and to assure adequate reliability. Thus, this is not necessarily an effective approach.